Process for the preparation of photoconductive light-sensitive materials comprising cds or cds. ncdco

ABSTRACT

Improved process for preparing photoconductive light-sensitive material wherein cadmium sulfide or cadmium sulfide/cadmium carbonate particles are dispersed in a resin binder, applied to a conductive support, and dried, the improvement comprising irradiating the dried photoconductive layer for a significant period of time.

Tim/med Mme Weir [72] Inventors liiatsuo Makiirm; [51] Im. Ci G03g 5/08 lwno Savvmo; Yoshihiiw Yamada; Jun [50] Field of Search 96/1, 1.5; 0110mm, all 05 Oriawara-sini, liianagawa, 252/5 01 Japan 21 Appl. 116. 795,806 References Cited! [22] Filed Feb. 3, 1969 UNITED STATES PATENTS Patented 09926 1971 3,249,430 5/1966 Metcalfe er a1. 96/1 Assisnee Fuji Photo Film 3,385,699 5/1968 Honjio eta]. 96/1 KEWWWBJQPW 3,506,595 4/1970 Makino 6! 252/501 [321 Priority Feb. 2, 1968 [33] Japan Primary Examiner-George F. Lesmes I [31] ASSI'SIGIII Examiner-John COOPCI', Atmrney- Sughrue, Rothwell, Mion, Zinn & Macpeak [54] PROCESS FOR THE PRIETARATION 01F PHOTUCIDNDUCTHVE LHGHT-SENMTIWE ABSTR A61 I d f a h t d MATERIALS coMPmsmG CdS 0190mm .Y Pmess 9 P O Odom tlve light-sensitive material wherein cadmium sulfide or cad- 2 Drawing g mium sulfide/cadmium carbonate particles are dispersed in a resin binder, applied to a conductive support, and dried, the [52] U.S.CE[ .1 96/].5, improvement comprising irradiating the dried photoconduc- 252/501 tive layer for a significant period oftime.

SURFRZCE POTEHTIAL (VOLT) REPEATING NUMBER BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates generally to a process for preparing photoconductive light-sensitive materials, and more particularly to a process for preparing photoconductive lightsensitive material having stabilized characteristics under repeated use.

2. Description of the Prior Art Hitherto, there have been lmown various kinds of electrophotographic light sensitive materials. They may generally be divided into vacuum evaporation types and binder types. For example, as the former type of photoconductive light-sensitive materials there are light-sensitive materials prepared by forming a light-sensitive layer of vitreous selenium on a conductive support by vacuum evaporation. As the latter type of photoconductive light-sensitive materials there is a light-sensitive material prepared by forming on a support fine powders of p'hotoconductor dispersed in a resin binder. The photoconductive light-sensitive material prepared in the present invention belongs to the latter type.

Typical examples of finely powdered photoconductors generally used are zinc oxide and cadmium sulfide. However, since zinc oxide has a specific sensitivity in the range of 3750-3900 A, the material is unsuitable for electrophotography utilizing light in the visible spectrum range. Accordingly, it is necessary to extend the spectral sensitivity thereof into the visible spectrum range. To do this, it has been proposed, for example, to add a dye to the photoconductive light-sensitive composition (see [1.5. Pat No. 3,052,540).

The same concept involving cadmium sulfide and dye sensitization is described in the "Journal of the Optical Society of America; Vol. 46, 13(1956).

However, zinc oxide sensitized by a dye, as described above, has such faults. The sensitivity is not sufficient, the preexposure effect and the fatigue (as general characteristics of a zinc oxide type photoconductor) are large, and its properties are unstable.

On the other hand, a photoconductive light-sensitive layer comprising a binder having dispersed therein fine powders of cadmium sulfide has other faults. For instance, the sensitivity is reduced as thickness increases; therefore the sensitivity is reduced when the thickness of the layer is increased in order to increase the initial surface potential to obtain sufficient electrostatic contrast of the electrostatic latent image formed on the light-sensitive layer. The response speed to photoconductive current is also slow.

SUMMARY OF THE ENVENTION By irradiating a dried photoconductive powder-containing layer under light for an extended period of time, photoconductive light-sensitive materials illustrating greatly improved properties are obtained. The overall process environment wherein the improved irradiation step finds particular applicability comprises dispersing powders of a photoconductor comprising cadmium sulfide or cadmium sulfide and cadmium carbonate having the general formula CdS-nCdCO wherein n is a positive number less than 4, in a resin binder, applying the dispersion thus formed to a conductive support and thus drying the photoconductive layer thus formed. The present invention thus has as its object the provision of a process for preparin g a photoconductive light-sensitive material illustrating none of the faults heretofore encountered by the prior art materials, described in the description of the prior art.

BRlEF DESCRiPTlON OF THE illl lAWlNGS FIG. l is a plot of surface potential in volts versus the number of repeating process sequences.

FIG. .2 in in plot representing the light fatigue versus the time ofexposure to light.

2 DESCRIPTION OF THE PREFERRED EMBODIMENTS Upon considering that conventional photoconductors have various insufficient points in practical use, the inventors have investigated the preparation of improved photoconductors which are satisfactory from the viewpoint of their electrophotographic characteristics and the preparation thereof.

The inventors have prepared a photoconductor of a physiochemically bonded system of cadmium sulfide and cadmium carbonate CdS'nCdC0 (0 n 4) to improve the characteristics of cadmium sulfide, and have :found that this material has excellent properties for use as an electrophotographic light-sensitive material. The photoconductor thus prepared has excellent merits, as a high photosensitivity, a small preexposure effect, deterioration of characteristics upon repeated use is small, the material is thermally stable, it has a long life and it can be used efiectively when it is charged both at positive and in negative polarity. Further, the electrostatic contrast thereof is good, the response speed of photoconductive current is high, and the material is easily prepared.

The photoconductive light-sensitive material of this invention may be utilized in a number of fields but is usually employed as electrophotographic light-sensitive material, and hence the invention will hereinafler be explained in detail mainly from the viewpoint of usage as electrophotographic light-sensitive material.

Furthermore, there have been developed photoconductors mainly composed of cadmium carbonate and cadmium sulfide wherein characteristics such as the intrinsic sensitivity of the finely powdered photoconductor have been increased and the spectral sensitivity range has been enlarged. This was done by incorporating selenium or a compound thereof in the photoconductor, by incorporating iodine or a compound thereof in the photoconductor, or by incorporating in the photoconductor a dye capable of absorbing radiant energy to thereby transfer the energy to the finely powdered photoconductor.

Now, the novel photoconductive light-sensitive material developed by the inventors will be explained in detail.

The structure of the photoconductive fine powder mainly composed of cadmium carbonate and cadmium sulfide is not clear, but it is at least clear that the material is not a simple mixture of time powders of cadmium sulfide. This photoconductor may be prepared by simultaneously adding dropwise sulfur ions and carbonate ions to an aqueous solution of a water-soluble cadmium salt, or by adding sulfur ions to a suspension of fine powders of cadmium carbonate to convert a portion of the cadmium carbonate to cadmium sulfide.

As illustrative cadmium salts there are cadmium halides, cadmium sulfate, cadmium nitrate, etc. As illustrative carbonates, there are sodium carbonate, potassium carbonate, ammonium carbonate, etc.

Examples of preparing the pliotoconductor are given below.

Preparation 1 The following solutions were prepared:

Solution A: 212 g. of sodium carbonate in 1.5 liters of distilled water;

Solution B; 457 g. of cadmium chloride (2 Veil-I 0) in 1.0

liter of distilled water; and

Solution C; 78.1 g. ofsodium sulfide (anhydrous) in 0.2 liter of distilled water.

Into solution A there was suspended, with stirring, fine powders of silica (trade name Aerosil made by Degussa). Solution B was added dropwise to this suspension to form white precipitates of cadmium carbonate. While further suspending Aerosil and cadmium carbonate, solution C was added dropwise to the system, whereby a portion of the cadmium carbonate particles were converted into cadmium sulfide (a yellow precipitation).

The yellow precipitates thus formed were washed with water and dried about 30 hours at 70 C. Thereafter, the precipitates were subjected to a low temperature heat treatment at 200 C. for about 24- hours. The powder obtained could be used as the base powder in the present invention.

Preparation 2 A mixture of fine powders of cadmium carbonate (0.1-0.2 microns granular size) and a fine sulfur powder (mixing ratio of 70 to 30 by weight) was heated to about 450 C. to provide fine powders composed of cadmium carbonate and cadmium sulfide. By X-ray diffraction analysis, it was confirmed that cadmium sulfide was present in the cadmium carbonate as a hexagonal phase, a cubic phase and an amorphous phase. An analysis of the composition confirmed that the powder had the composition CdS'l .5CdCO Other materials may be added to these powders, as long as they do not degrade the photoconductive properties thereof. For instance, by adding bentonite, fine silica powders, diatomaceous earth and the like to a reaction system when the fine particles of cadmium sulfide and cadmium carbonate had been precipitated, the amount of fine powder formed could be controlled, and the formation of cakes during the drying step could be prevented.

if desired, necessary components may be added to the photoconductor composition to such extent that the photoconductive properties are not degraded or photoconductive properties can even be enhanced. Further, fine powders inorganic or organic compounds having no spectral absorption in the spectral sensitive region of the phosphor may be added. As mentioned above, fine silica powders are effective as such additives. As other illlustrative additives, there are diatomaceous earth, zinc oxide, zinc sulfide, titanium oxide, aluminum oxide, magnesium oxide, etc. Further, a part of the sulfur in the cadmium sulfide base powder may be replaced by selenium.

Other embodiments developed by the inventors are composed of the aforesaid photoconductive powder and iodine or iodide, and these compositons are also effective. The preparation of these photoconductive powders will be further explained with reference to the following example.

Preparation 3 Powders composed of cadmium sulfide and cadmium carbonate (CdS-l.5CdCO,) were dispersed in ethyl alcohol and then an ethyl alcohol solution of iodine (containing 40 g. of iodine in I000 mi. of ethyl alcohol) was added dropwise to the dispersion to absorb iodine on the particles composed of cadmium sulfide and cadmium carbonate. After settling the system for several hours, the supernatant liquid was removed, and the residue was subjected to vacuum drying to provide fine powders capable of being used in the present invention.

As iodine compounds which can be added as above, there are lithium iodide, magnesium iodide, beryllium iodide, bismuth iodide, tungsten iodide, cesium iodide, strontium iodide, tin iodide, potassium iodide, cadmium iodide, antimony iodide, aluminum iodide, zinc iodide, and the like. These compounds are soluble in water or organic solvents. As the most practical embodiment, a solution of the above compound is contacted with the photoconductive powder. By exposing the powder to the vapor of the above compound, the compound may be absorbed on the surfaces of the powders and diffused into the powders. This is perhaps most useful when the iodine compound used is not soluble in water and organic solvents, such as lead iodide. Thus, by heating lead iodide to form the vapor thereof and baking the powders of the photoconductor in the vapor, lead iodide can be added to the powders.

To obtain the photoconductor used in the present invention, a dye may be added to the fine powders of cadmium sulfide or the fine powders composed of cadmium sulfide and cadmium carbonate to increase the intrinsic sensitivity thereof and/or to enlarge the spectral sensitivity range. Typical examples of such dyes are phthalenic dyes such as Eosine, Rose Bengale, Fluorescence, Phloxine, and Ethyle Eosine; triphenylmethanic dyes such as Malachite Green, Crystal Violet, and Brilliant Green; cyaninic dyes such as Dicyanine, Cryphtocyaninc. pinacysnol. neocyanine, and merocyanine; and others such as Rhodamine B and Methylene Blue. The dye may be used alone or mixtures thereof can be added to the fine powders of cadmium sulfide or the fine powders composed of cadmium sulfide and cadmium carbonate.

The manner of addition of the aforesaid dyes is the same as for the case of adding iodine or an iodine compound. When the dye is soluble in water, fine powders of the photoconductor are preferably added to an aqueous solution of the dye to provide a slurry, which is dried.

When the dye used is soluble in an organic solvent, the dye is added in a similar manner by the aid of the organic solvent. The thus-obtained photoconductive base powder containing iodine, iodides (or the dye-sensitized photoconductive powder) is dispersed into a binder material to form a photoconductive light-sensitive material.

The photoconductive light-sensitive material thus obtained has many advantages, i.e., the response speed to photocurrent is high, the electrostatic contrast is good, the material is thermally stable, highly durable, and the material can be used effectively in the cases of both positively charging and negatively charging. However, there still remain such faults as the fact that the characteristics thereof are considerably degraded under repeated continuous use and also, preexposure effect is observed to some extent.

Thus, one further object of the present invention is to provide a process for preparing a photoconductive light-sensitive material comprising cadmium sulfide and having improved properties, in particular, a high stability under continuous, repeated use.

According to the present invention, there is provided a process for the preparation of photoconductive light-sensitive material which comprises dispersing a photoconductive powder mainly comprising cadmium sulfide or a photoconductive powder mainly composed of cadmium sulfide and cadmium carbonate in a high-resistance resin binder, applying this dispersion to a conductive support, drying, and irradiating the photoconductive layer thus formed with light for a long period of time.

It has long been known that when a conventional photoconductive layer of amorphous selenium (formed by vacuum evaporation) is exposed to light for a long period of time, the properties thereof are degraded. The inventors surprisingly have found that when the photoconductive layer comprising cadmium sulfide prepared by the process of this invention is light-exposed for a long period of time, the sensitivity thereof may be reduced slightly, but that the degradation in the other characteristics typically caused by continuous, repeated usage is markedly improved.

The invention will now be explained with reference to the accompanying drawings wherein:

FIG. 1 is a graph showing the variation in the initial potential of a photoconductive layer exposed to light for a long period of time and a comparative sample both under repeated use.

FIG. 2 is a graph showing the relationship between the light fatigue of a photoconductive light-sensitive layer and the time of light exposure.

FIG. 1 shows the results of a process series of steps which involved electrostatically charging the photoconductive layer of the sample by means of a corona-discharging means to which a direct current potential of 7.0 kilovolts was connected, measuring the surface potential (initial surface potential) of the photoconductive layer immediately after charging, discharging the eletrostatic charges on the layer by exposing the layer to light, charging again, measuring the surface potential, and then repeating the procedure. In the figure, the relationship between the number of repeats and the initial surface potential is shown. In this case, the repeating time was 10 seconds.

In FIG. 1, curve a represents the case where the sample was exposed to light for 96 hours at a position of 10 cm. from a white fluorescent lamp of 20 watts; curve b represents the case where the sample was exposed for 48 hours under the same conditions; and curve 0 represents the case where the sample was not exposed to light at all.

As is clear from the results shown in FIG. l, the variation in the initial potential of the sample caused by continuous, re peated usage was prevented to a large extent by exposing the photoconductive layer thereof to light for a long period of time.

To further explain H0. 2, the surface of the samples was exposed to light (white fluorescent lamp) for 20 minutes, an illumination of 2000 luxes being used. The samples were then charged after l seconds, and the initial surface potential was measured. The ratio of the value measured with respect to the initial surface potential was measured. The ration of the value measured with respect to the initial surface potential of the photoconductive layer after storage in the dark for a period of time is defined as the degree of light fatigue. MG. 2 is a graph showing the relationship between the light fatigue and the period of time which the photoconductive layer was exposed to light. it is clear from FIG. 2 that the light fatigue improved as the amount of exposure increased and the saturation occurred at some level of exposure.

in the present invention, ultraviolet rays or visible rays are preferably used for exposure. The exposure time may be in the range of l to 200 hours. The exposure value is preferably more than 5 X l0 lux. hour.

The binder materials employed in this invention can be, for example, polystyrene, silicone resins, acrylic ester polymers, methacrylic ester polymers, polymerized butyl methaorylates, vinyl polymers and copolymers cellulose esters and ethers, and allryd resins.

It is found that preferable proportion of binder and phosphor is within 80-40 percent by volume the binder to -60 percent by volume phosphor.

The invention will now he explained in more detail with reference to the following examples.

Example 1 l dispersion having the following composition was prepared:

Cadrnium sulfide powder 120 1g. Megicron No. 200 clear 120 (solid content 60 g.) Magicron No. 200 thinner 60 ml.

"Thcrmoscttittg acrylic resin lacquer iiansai Paint C(L, Ltd.)

The dispersion thus prepared was applied to an aluminum sheet at a thickness of 40 microns. The sheet was allowed to dry and subjected to heat treatment at 130 C. for minutes. The product is an elcctrophotographic light-sensitive material having a metallic backing and a photocondnctive insulating Exam pie 2 The same procedure as in example l was repeated using a dispersion having the following composition: Cadmium sulfide cadmium carbonate powder CdSzLll'LdCO 120 g. Mugicron No. 200 clear H0 5. (solid content 60 g.) Muglcrnn No. 200 thinner 60 ml.

The results were substantially the same as those in example .l.

Example 3 The following solutions were prepared: Solution A: 21.2 g. of sodium carbonate dissolved in 1.5

liters ofdistilled water;

Solution B: 457 g. of cadmium chloride (2 Val- 0) dissolved in 1.0 liter of water; and

Solution C: 78.1 g, of sodium sulfide (anhydrous) dissolved in 0.2 liter ofdistilled water.

Solution A was mixed with 250 g. of the line powders of silica Aerosil (made by Degussa) with stirring to disperse the fine powders in the solution. Solution B was slowly added dropwise to the dispersion in order to form a white precipitate of cadmium carbonate. Further, while dispersing Aerosil and the cadmium carbonate, solution C was added dropwise to the dispersion, whereby a part of cadmium carbonate was converted to cadmium sulfide. o

The yellow precipitates formed were washed with water and dried at C. for about 30 hours. Thereafter, by maintaining the line powders for about 24 hours at 200 C., the powders were subjected to a low temperature heat treatment. The line powders obtained were designated as powder D."

into ethyl alcohol there was dispersed one part by weight of powder D and, while stirring, a solution of 0.2 parts by weight cadmium iodide dissolved in ethyl alcohol was added dropwise to the dispersion, whereby cadmium iodide was adsorbed on powder 1). After allowing the system to settle for a few hours, the supernatant liquid was removed, the powders were dried at 70 C. overnight and then heat-treated at 200 C. overnight. The line powders thus obtained were designated as powder E."

The powder E thus obtained was dispersed in one part by weight of a thermosetting acrylic resin and the dispersion was applied to an aluminum sheet or an aluminum pipe at a thickness of 20-b0 microns to provide a electrophotographic light-sensitive layer capable of repeated use.

The surface of the layer was exposed to a 20-watt white fluorescent lamp at a distance of 10 cm. for a long period of time (10-30 hours). Thereafter, the layer was repeatedly subjected to an electrophotographic process comprising charging, exposing, developing, transferring, cleaning, and charging.

In the above experiments, it was confirmed that the varia tion of the surface potential or the example charged was much less when repeatedly used in the sample previously exposed to light than in the sample unexposed. The residual potential (after exposure) was substantially the same in both cases.

Example 4 To one part by weight of powder E in example 3 there was added an ethyl alcohol. solution of 001-01 part by weight of Brilliant Green. The mixture was stirred and dried. The powder obtained was designated as "powder F.

The same procedure as in example 33 was repeated while using powder l instead or powder E to provide an elec trophotographic light-sensitive layer.

The surface of the layer was exposed to a 20-watt white fluorescent lamp from a distance of i0 cm. therefrom for a long period of time (Ml-2'50 hours). Thereafter, the layer was repeatedly subjected to an electrophotographic process comprising charging, exposing, developing, transferring, cleaning, and charging. The results were substantially identical to those of example 3.

To briefly amplify upon the material heretofore offered in the specification, the photoconductive particles utilized in the present invention should preferably have a particle size less than 1.5 microns.

The amount of iodide which should be incorporated in the photoconductivc particles of the present invention can generally have a maximum value of 0.3 moles of iodine per mole of cadmium, with a most preferred range being equal to less than 0.l mole ofiodine per mole of cadmium.

With respect to the incorporation of a dye into the photoconductive particles of the present invention, the amount of dye must be less than 0.1 parts by weight, preferably in the area of 0.05 part by weight of the dye. It will be appreciated that very minor amounts of the iodine or dye can affect the end photoconductive particle.

With respect to partially replacing sulfur with selenium, the maximum permissible substitution is percent.

To further define the resin resistivity of the present invention, this is most preferably greater than 10 ohms. cm. With respect to the required drying time and temperature used in forming the particles of the present invention, these will be decided by the characteristics of the binder used.

The coating thickness used is generally less than 150 microns with a most preferable range being from 1080 microns.

With respect to the light exposure which is used in the present invention, generally an intensity within the range of from 1000 to 1,000,000 lux. hour may be used. The time for the exposure is most preferably within the range 2-100 hours.

In preparing Fl'G. 2, a dark storage time of 24 hours was used.

in example 3, approximately 60 percent of the cadmium carbonate was converted to cadmium sulfide. Further, substantially 100 percent of the cadmium iodide dissolved in the ethyl alcohol was absorbed on powder D. Two parts by weight of powder E described in example 3 was dispersed in one part by weight of the thermosetting acrylic resin.

In all examples, a photoconductive powder having a size of the range 0.1-0.4 microns was used.

What is claimed is:

1. In a process for the preparation of a photoconductive light-sensitive material which comprises dispersing powders of atphotoconductor selected from the group consisting of cadmium sulfide and cadmium sulfide/cadmium carbonate combination having the general formula CdS. nCdCo wherein n is a positive number no larger than 4, said powders being dispersed into an insulating resin binder,

applying the thus-formed dispersion to a conductive support whereby a photoconductive layer is formed, drying the photoconductive layer thus formed, the improvement which comprises irradiating the dried photoconductive layer with light at an intensity greater than about 5 X lux. hr. for a period of time within the range of from about 1 to about 200 hours.

2. The process of claim 1 wherein said photoconductive powders contain a member selected from the group consisting of iodine and an iodide compound to increase the sensitivity.

3. The process of claim 2 wherein said iodide compound is selected from the group consisting of lithium iodide, magnesium iodide, beryllium iodide, bismuth iodide, tungsten iodide, strontium iodide, tin iodide, potassium iodide, cadmium iodide, antimony iodide, aluminum iodide, and zinc iodide.

4. The process of claim I wherein said photoconductive powders additionally contain a dye to increase the sensitivity.

5. The process of claim 4 wherein said powder of a photoconductor has absorbed thereon up to about 0.1 percent by weight of a said dye.

6. The process of claim 1 wherein said resin binder has a resistivity greater than 10 ohms. cm.

7. The process of claim 1 wherein said light has an intensity within the range of from about 1000 to about 1,000,000 lux. hour and the duration of light exposure is within the range of from about 2 to about 100 hours.

8. The process of claim 1, wherein the photoconductor are the cadmium sulfide.

9. The process of claim 1, wherein the powders of the photoconductor are the cadmium sulfide/cadmium carbonate.

10. The process of claim 2, wherein the photoconductive powders contain the iodide compound, and the iodide com pound is a metal iodide.

11. The process of claim 1, wherein the proportion of binder material to photoconductor is to 40 percent by volume of binder to 20 to 60 percent by volume of photoconductor.

12. The process of claim 11, where the binder is selected from the group consisting of polystyrene, silicone resins, acrylic ester polymers, methacrylic ester polymers, polymerized butyl methacrylates, vinyl polymers, vinyl copolymers, cellulose esters, cellulose ethers, and alkyd resins.

13. A photoconductive light-sensitive material produced by the process of claim 1. i

powders of the 

2. The process of claim 1 wherein said photoconductive powders contain a member selected from the group consisting of iodine and an iodide compound to increase the sensitivity.
 3. The process of claim 2 wherein said iodide compound is selected from the group consisting of lithium iodide, magnesium iodide, beryllium iodide, bismuth iodide, tungsten iodide, strontium iodide, tin iodide, potassium iodide, cadmium iodide, antimony iodide, aluminum Iodide, and zinc iodide.
 4. The process of claim 1 wherein said photoconductive powders additionally contain a dye to increase the sensitivity.
 5. The process of claim 4 wherein said powder of a photoconductor has absorbed thereon up to about 0.1 percent by weight of a said dye.
 6. The process of claim 1 wherein said resin binder has a resistivity greater than 108 ohms. cm.
 7. The process of claim 1 wherein said light has an intensity within the range of from about 1000 to about 1,000,000 lux. hour and the duration of light exposure is within the range of from about 2 to about 100 hours.
 8. The process of claim 1, wherein the powders of the photoconductor are the cadmium sulfide.
 9. The process of claim 1, wherein the powders of the photoconductor are the cadmium sulfide/cadmium carbonate.
 10. The process of claim 2, wherein the photoconductive powders contain the iodide compound, and the iodide compound is a metal iodide.
 11. The process of claim 1, wherein the proportion of binder material to photoconductor is 80 to 40 percent by volume of binder to 20 to 60 percent by volume of photoconductor.
 12. The process of claim 11, where the binder is selected from the group consisting of polystyrene, silicone resins, acrylic ester polymers, methacrylic ester polymers, polymerized butyl methacrylates, vinyl polymers, vinyl copolymers, cellulose esters, cellulose ethers, and alkyd resins.
 13. A photoconductive light-sensitive material produced by the process of claim
 1. 